Propeller



'April25,1939. T. OLLER 2,156,133

PROPELLER Filed June 16, 1,936

INVENTOR ATTORNEY 4/ 771500025 H. 77?0LLER Patented Apr. 25, 1939 UNlTEl STATES PATENT OFFICE ,l'normnn Theodore B. Trailer, Akron, Ohio Application am 16, 1936, serial No. 85,472

13 Claims. (01. 110-112) This invention relates 'to propellers, and more especially it relates to rotary propellers or airscrews comprising two or more blades such as may be used,for example, for propelling vehicles or for creating a velocity head of air, as in blowers and'pumps.

Propellers of the character mentioned have blades that are cambered on one or both sides and provided with a rounded nose or leading edge. Such blades, as heretofore constructed, required to have a definite minimum area for a determinate'load, and there were definite limits to the maximum load that the blades could exercise in an emcient manner. The aforesaid limitations of prior propeller blades reduces their usefulness in many ways and it is to the improve ment of these conditions that the present invention is directed.

The chief objects of the invention are to pro-' 2o vide an improved propeller blade capable of greater unit-area load than obtained in propeller blades heretofore provided; to provide an improved propeller blade that will permit reduced speed 01' rotation of the ropeller without sacriincidental to the operation of the propeller; to provide a propeller blade design that permits the blade to be madein narrower width and greater thickness, thus providing greater strength and of velocities. Other objects will be manifest as the specification proceeds.

It is well known that the specific load on propeller blades of the character mentioned can be materially increased if the layer of fluid (air) immediately adjacent a particular region of the surface of the rotating blade-is energized or is removed therefrom. It has been proposed heretofore to accomplish this result by the use of suction for removing fluid from the said surface of the blade, and, alternatively, by the use of fluid pressure for energizing or breaking up the layer of air on the said surface of the blade, in either fice of the efliciency ther of;"to reduce the noise resulting in less vibration while rotating; and to provide a propellrhaving a wider useful range case the amount of fluid removed from the blade mechanism is expensive, complicated and frequently out of order.

In the present invention the forces set up by the rotation of the propeller blades are utilized for effecting a movementor flow of air in ducts 6 in the said blades as a means for sucking air from the surface of the blades and/or ejecting it therefrom. The invention also contemplates the controlling of the flow of air in the ducts in the blades, and the taking in and discharging of 10 air from the ducts without essential loss of power.

of the illustrative embodiments of the invention shown in the accompanying drawing,

Figure 1 is a side elevation of a propeller constituting one embodiment of the invention, one 15 of the blades thereof being shown in transverse including an automatic control for fluid in the duct in' the blade;

Figure 5 is a section taken on the line 5-5 of 25 Figure 4;

Figure 6 is a fragmentary elevation of a propeller constituting the invention including means for manually controlling the flow of fluid in the duct in. a blade; and a 30 Fig. 7 is a section taken on the line Figure 6.

Referring to the drawing, in Figure 1 thereof is shown a propeller of the type used in air pumps and blowers, said propeller comprising a hub por- 35 tion In and a plurality of radially extending blades I I, I i. The latter are of the type that have the major portion of their length, at least, of aerofoil section, that is, they have a blunt nose or leading edge, a cambered upper or suction face, 40

of I

and a lower or pressure face of lesser camber, said faces meeting in a relatively thin, sharp, trailing edge. The blades ii are made of metal, wood or Bakelite and are so shaped that their pitch is smaller adjacent their tips than near the hub, 45 the blades so shapedas to enable easy fastening and adjustment'in the hub, and providing a gradual transition from the region of aerofoil section to the portion that is mounted in the hub:

- Formedinteriorly of each blade II is a passage or duct l3 that is disposed longitudinally of the bladeiand radially pf the hub III, the ends of said duct terminating in respective slots 14, IS in the upper-or suction faceof the aerofoil portion of the blade, The slot i5 is disposed relatively near the tip of the blade and constitutes the delivery orifice of the duct IS. The slot I4 is disposed relatively near the hub ill of the propellerand 7 radially outwardly with relation to hub Ill, with the result that said air is forcibly ejected from the slots ii of the blades and concurrently air is drawn into the ducts, through slots H, by the resulting suction. Another factor that contributes to the aforesaid result'is the differential fluid pressures that obtain on the suction side of the blade longitudinally thereof. Because the speed of the propeller blade is greater at its tip than at its hub, the suction on the upper or cambered face of a suitably formed propeller may be greater in the region of slot l5 than it is inthe region of slot i4. However, the centrifugal force is relied upon primarily to achieve-the result desired.

By removing air from the surface of the propeller blade at one region of its cambered-face and ejecting it from another region thereof, the thin fllm' of air clinging to said surface is removedor energized, with the result that more efllcient-operation of the propeller is achieved.

In the embodiment of the invention shown in Figure 2, the cambered face of the propeller blade Ii is formed with a slot II that is disposed in the aerofoil portion of the blade but relatively near the hub It, said slot communicating with a duct l8 that is formed interiorly of the blade and extends longitudinally thereof for a substantial distance, said duct terminating in a discharge orifice I! on the margin of the blade at the trailing edge thereof. In like man- .ner a second slot20 is formed in the same face -of the blade, relatively near the tip thereof, said slot. communicating with a duct 2| that terminates in a discharge orifice 22 onthe trailing edge of the blade.

Centrifugal force set up in the air in ducts l8, 2| during rotation of the propeller causes said air to be elected from the blade through orifices 'II, 22, and concurrently airis drawn into the ducts, by suction, through the respective surface slots l1 and 20. Discharge 'of the air at the trailing edge of the blade performs the useful function of assisting in the propulsion of the blade by reducing the torque of the motor that drives the propeller.

terminate on the margin 'of the blade at the tip,

In the embodiment of the invention shown in Figure 3, the propeller blades H are each formed a plurality of parallel, longitudinally extending, internal ducts 24, 24, the inner ends-of which terminate in respective slots 25, 25 that open onto the cambered face of the blade, said slots 25 being arranged in a row longitudinally of the blade. At their outer ends the ducts 24 thereof in delivery orifices 23, .26, the latter being somewhat flared as shown, to diifuse the air ejected therefrom.

s In the embodiment of the invention shown in Elgurmi, each of the blades ll of the propeller is formed in its cambered face witha'slot 24 in the aerofoll portionof the blade relatively near the hub HF, and a slot 29 disposed relatively a near the tip of the blade.

Formed interiorly of the blade il is a relatively short, longitudinally disposed duct 30' that extends radially inwardly from the slot 23 to a valve 3| that is located close to the hub HF, and a relatively long, longitudinally extending duct 30 that extends from the valve 3i to the slot 29. The valve 3! is an automatically operating check valve that is yieldingly urged by a compression spring 32 onto a valve seat 33, said valve being slidably mounted upon a headed stem 34 carried by a body member 35 that is threaded into the structure of the blade. The sprin valve to open automatically when there is determinate diiferential fluid pressure in the ducts 30, 30 which differential pressure is established when the rotation or the working condition of the propeller reaches a determinate condition. When the valve is open, ducts 30*, 30' are in communication and air is drawn into the ducts through slot 28 and ejected therefrom through slot 29 in the manner of the embodiment shown in Figure 1. The valve 3| 'is positioned as close to the hub 10 as possible so as not to be materially influenced by the rotation of the propeller.

The embodiment of the invention shown in Figure 6 is substantially similar to that shown in Figure 4 except that its valve is arranged for manual operation. As shown in Figure 6, the propeller blade li is formed with surface slots 31, 38 that communicate with the outer ends of interiorly disposed ducts '39, 39", the

latter terminating at their inner ends on oppo-' 42 of a solenoid 43, the latter being mounted in a suitable recess in the blade and being retained therelnby a threaded cap 44. A compression 32 is of proper strength to permit the spring 45 is mounted between the valve 40 and the adjacent end of the,solenoid,'said sprinS normally urging the valve into seating engagement with the seat 4|. For operating said solenoid, a pair of conductor wires 43 are provided, which wires extend throu h a duct 41, formed axially of the propeller hub I0 to a suitable battery 43 and operatingswitch 49 disposed at a convenient point removed from the propeller. The arrangement is such that an operatormay open the valve 40 at will, andv thus permit the slots 3'l, 38 and connecting ducts to function in the manner described.

The invent-ion increases the efliciency of propeller blades, is simpler than means heretofore provided for achieving a'similar function,

achieves the other advantages set out in the foregoing statement of .objects. odification may be resorted to without depa ing from the spirit of the invention or the scope of the appended claims.

What is claimed is: l.- A propeller of the character described comprising a blade haying a major portion of aeroioil section and formed interiorly with a duct that extends longitudinally of the blade and ra-, dially of the axis of the propeller, the inlet end of said duct being nearest the axis of the pro,- peller and opening onto one region of the aerofoil portion of the blade on the canibered side thereof, removed from the leading edge thereofto avoid scoop effectyand the delivery end of the duct opening onto another region of ,the aerofoil portion of the blade more remote from and H minates in a slot in the cambered face of the,

the axis of the propeller, and so constructed and arranged that rotation of the propeller efiects a flow of fluid in the duct, which fluid enters one end of the duct and discharges from the other end thereof for energizing the layer of the same fluid on the surface of the blade, the duct openings being relatively small so as not materially to reduce the effective area of the blade.

2. A combination as defined in claim 1 in which the delivery end of the duct opens onto the cambered face of the blade.

3. A combination as defined in claim 1 in which the delivery end of the duct opens onto a margin of the blade.

4. A combination as defined in claim 1 in which the delivery end of the duct opens onto the tip of the blade.

5. A combination as defined in claim 1 in which the delivery end of the duct opens onto the trailing edge of the blade.

6. A propeller of the character described comprising a blade formed interiorly with a duct that has its respective ends opening onto the surface of the blade at spaced apart points thereon, and so arranged that rotation of the propeller effects a flow of fluid longitudinally in said duct, and means for obstructing the flow of fluid in said duct until the pressure difference between the two openings of the duct reaches a determinate value.

7. A propeller of the character described comprising a blade formed interiorly with a duct, the ends of which open onto the surface of the blade at spaced apart points thereon, and so arranged that rotation of the propeller effects a flow of fluid longitudinally in said duct, and a check valve in said duct operated automatically by differential fluid pressure on opposite sides thereof.

8. A propeller of the character described comprising a blade having a 'major portion of aerofoil section and formed interiorly with a duet, the respective ends of which open onto the surface of the blade at spaced apart points of said aerofoil portion thereof, and so arranged that rotation of the propeller effects a flow of fluid longitudinally in said duct, a check valve adapted to obstruct the flow of fluid in said duct, and means for manually controlling the operation of the check valve from a point removed from the propeller, said means comprising a solenoid in the blade, and electrical conductor wires extending axially through the hub of the propeller for conducting operating current to the solenoid.

9. A propeller of the character described comprising a blade having a major portion of aerofoil section, and formed interiorly with a longitudinally extending duct of which one end terblade in the said aerofoil portion thereof, and the other end terminates in a flared orifice on the margin of the blade to effect diffusion of fluid ejected therefrom by reason of the rotation of the propeller.

10. A propeller of the character described comprising a blade having a major portion of aerofoil section, and means for withdrawing fluid into the blade from the surface of the cambered side of said aerofoil portion, removed from the leading edge to avoid scoop effect, and expelling it from the blade on the same side of said aerofoil portion at a region removed from the point where it enters the blade, said means comprising openings in the blade of such small size as not materially to reduce the effective area of the blade.

11. A propeller of the character described comprising a blade having a major portion of aerofoil section; and formed interiorly with a longitudinally extending duct that has its ends opening onto the surface of the blade at spaced apart points of said aerofoil region, the inlet end of said duct, at least, being located on the cambered side of said blade, said duct being so arranged that rotation of the propeller effects a longitudinal flow of fluid therein, and means located in said duct relatively close to the hub of the propeller for regulating the flow of fluid in the duct.

12. A propeller of the character described comprising a blade having a major portion of aerofoil section, means for removing air locally from the surface of the blade, in the said aerofoil region, solely by suction as the propeller rotates.

and a duct in said blade having a discharge orifice at the surface thereof for discharging said air from the blade, said orifice being so located in the aerofoil region of the blade and so shaped I as to reduce losses in the efliciency of the propeller due to the energy of the discharging fluid.

13. A propeller of the character described comprising a blade having a major portion of aerofoil section formed interiorly with a curvilinear duct, the respective ends of which open onto the surface of the blade at spaced apart points longitudinally of said aerofoil portion, and so arranged that centrifugal force set up by rotation of the blade effects a flow of fluid longitudinally of the duct, an intermediate portion of said duct being disposed nearer the hub of the propeller than the inlet or outlet of the duct, and means located in the aforesaid intermediate portion of the duct for regulating the flow of fluid therein.

THEODORE H. TROLLER. 

